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Dear Romy,

I have been reading the threads on GoodSoundClub about your journey with development of the Melquiades and Super Melquiades amplifiers.  They are very interesting to me.  I am pleased that your purpose was to produce a particular amplification result that was in your "mind-eye" so to speak to drive your horn speakers and that you did not feel constrained to operate within what may have been conventions.

I hope that you do not mind answering some of my questions about the Melquiades now that you have some time of experience using them.

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The thread mentions:
I feel that 6E5P has own very interesting "puss" as Tony Soprano would describe it. This "puss" has something to do with dynamic viscosity and with its ability to sound "dynamically inelegant"....Some people see Melquiades as a 633C-base amp but I see the Melquiades as two stages SET with 6E5P driver...(if I am not mistaken about those PP) and he clamed that all of the amps, though sound differently still were able to express the 6E5P's signature....And since the 6E5P has quite a lot of own power (8W plate dissipation) then it asked to try it..

My question:
By "dynamic viscosity" do you mean the reluctance of an amplifier to be dynamic, i.e., the degree to which an amplifier sounds like it is bogged down, usually as a result of a poor rise time on transients, i.e., poor HF response, or a tube which is badly biased and loaded wrongly which is typical of many tone control stages in generic junk tube amps of the 1950 / 1960 era ?

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My understanding:
The curves for the 6E5P in tetrode are not a happy picture, but with triode connection it is okay. The 6C33C needs a lot of drive voltage since its amplification factor ( µ factor ) is very low.

My question:
The 6E5P is a russian tube and perhaps the 6CL6 is a near equivalent so instead of 6E5P could 6CL6 be used or even EL84 with equally good results ?

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My understanding:
It appears that the amplifier does bias a 6E5P with two gas tube regulated positive and negative voltages so that a negative voltage can be derived from a resistance divider and applied to the input tube grid.  While some holy audio priests say electro caps are forbidden ( unless perhaps thay are Black Gate or some other expensive brands) there is not much wrong with a Nichicon 1,000 uF cap to bypass cathodes.  At 100Hz they have 16 ohms of reactive impedance and there does not seem to be much evidence that their sonic signature can be detected in any AB tests.

My question:
Did you consider instead using an electrolytic and R used to provide cathode bias ?

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The thread mentions:
It was 10PM and it was like an instant bliss. It immediately reimbursed me with the exact sound that I was visualizing for quite along time. It slowed down the brutal and unreasonably fast dynamics, it harmonized and coordinated everything and set the correct relation and reasoning between the pitches, it created completely different phenomenal (!) bass and it basically made up the Milq sound in a way in which it is know today.

My understanding:
I can understand that by not using an input coupling cap the amplifier can produce quality bass.

My question:
Do you still believe that the brutal and unreasonably fast dynamics were corrected by the method of biasing the input tube?

My question:
If so, then could the same result be produced by using a standard 0.47 uF coupling cap with 150k bias R then -3dB = 2.2Hz, with no perceivable sonic difference.

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My understanding:
Milking voltage on a resistor is the use of what was known as grid leak biasing. This is where a 10Meg ohm R is used instead of say a typical 220k. There is always some very low current flow in a bias resistor feeding a grid, enough to usually cause about say -0.1V appear at the end of a 220k in a small power tube, and when 10M is used, the same current flows, but gives a voltage of -9V at the grid if the bias resistor is grounded at its other end.

My question:
Now that you have some time of experience with the amplifiers, have you found this to be a reliable biasing method ?

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My lack of understanding:
I am not sure of the output impedance for the amplifier, however, if we have a triode with Ra = 80 ohms, its load would be about 320 ohms at the anode, so the RL/Ra = 320/80 = 4.0, so the damping factor is 4. If the load match was for 6 ohms, then the OPT has a Z ratio = 320/6 = 53.3:1, so the source R = 80ohms/53.3 = 1.50 ohms, so if the speaker is 6 ohms, it is being fed from a source of 1.5 ohms, so if the speaker Z fell to 3 ohms at some F the output voltage would fall considerably.  The price for no FB is high output source resistance unless the OPT ratio is high. Higher than standard OPT ratios make an amp inefficient, but the higher the load used with a low load match the lower the THD/IMD becomes, and fidelity is improved.

My question:
Do you think that it could actually be this lower THD/IMD that has lifted the veil so to speak and simply the improved fidelity that is making you so happy with the results ?

Regards,
Peter.

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